| 摘要: | 本文觀測2022年11月斗六市和2023年3月至4月鹿林山PM2.5水溶性無機離子（Water-Soluble Inorganic Ions, WSIIs）濃度實時變化，並使用氣象條件和空氣品質監測資料、HYSPLIT逆推氣流軌跡，探討PM2.5高質量濃度時段，WSIIs濃度的變化趨勢及其來源。
斗六市區秋季高濃度PM2.5期間WSIIs受到NO3-主導，推論是NOₓ與OH的光化學反應導致。鹿林山區春季生質燃燒傳輸期間高濃度PM2.5的WSIIs以SO42-為主要污染物，與傳輸區域工業活動的SO₂排放有關。斗六市區在高濃度期間的NO3-濃度明顯上升，日間高濃度的NO₃⁻主要由交通和附近工業區排放的NOₓ與OH反應生成HNO₃，夜間則由白天生成的N₂O₅在高相對濕度和低風速環境下水解形成。斗六市區的氨氣非常充足，大氣氣膠WSIIs主要結合型態為(NH4)2SO4和NH4NO3。斗六市區每日下午的海風帶進海鹽氣膠，當不受其他來源影響時，估算的海鹽氣膠與酸性氣體反應造成的氯損失平均為28.8%。本文推論都市NO2-在夜間以液相反應形成，日間交通尖峰時段則由NO₃⁻還原成NO₂⁻。鹿林山區在生質燃燒傳輸期間，SO42-、NO3-、NH4+和K+濃度明顯增高， NO₂⁻則無法有效偵測到。鹿林山區高濃度事件主要污染來源為生質燃燒煙團，同時也觀察到山谷風事件，山谷風增加PM2.5和CO，但對污染貢獻沒有BB煙團顯著。鹿林山區的氨氣並不是非常充足，大氣WSIIs可能會出現(NH4)2SO4、NH4SO4、(NH4)3H(SO4)2、NH4NO3、NO3-（沒有與NH4+結合的NO3-）氣膠。
總結來說，斗六市區PM2.5高濃度的NO₃⁻來源以主要由交通和附近工業區排放的NOₓ與OH光化反應及夜間異液相反應為主。鹿林山區PM2.5高濃度則以生質燃燒煙團傳輸影響為主，山谷風的影響為次。
;This study observes the real-time variations in PM2.5 water-soluble inorganic ions (WSIIs) concentrations in Douliu City during November 2022 and at Lulin Mountain from March to April 2023. Utilizing meteorological conditions, air quality monitoring data, and HYSPLIT back-trajectory analysis, it investigates the trends in WSIIs concentrations and their sources during periods of high PM2.5 levels.
During the autumnal high PM2.5 concentrations in Douliu City, WSIIs were dominated by NO₃⁻, attributed to photochemical reactions between NOₓ and OH radicals. In contrast, during the spring biomass burning transport events at Lulin Mountain, SO₄²⁻ emerged as the predominant pollutant, linked to SO₂ emissions from industrial activities in the transport regions. A significant rise in NO₃⁻ concentrations was observed in Douliu during high PM2.5 periods, with daytime NO₃⁻ formed via reactions between NOₓ from traffic and nearby industrial emissions with OH radicals, producing HNO₃. At night, NO₃⁻ was generated from the hydrolysis of N₂O₅ under conditions of high relative humidity and low wind speeds. Ammonia was abundant in Douliu, and the major atmospheric aerosol WSIIs were in the forms of (NH₄)₂SO₄ and NH₄NO₃.Sea breezes transported marine aerosols into Douliu every afternoon. In the absence of other significant sources, the estimated average chloride loss caused by reactions between marine aerosols and acidic gases was 28.8%. It is hypothesized that urban NO₂⁻ was formed via liquid-phase reactions at night and was reduced to NO₃⁻ during daytime traffic peaks.
At Lulin Mountain, during biomass burning transport events, the concentrations of SO₄²⁻, NO₃⁻, NH₄⁺, and K⁺ markedly increased, whereas NO₂⁻ was undetectable. The primary source of pollution during these high-concentration events was biomass burning plumes, although valley winds were also observed. While valley winds increased PM2.5 and CO levels, their contribution to pollution was less significant compared to biomass burning plumes.Ammonia was not as abundant at Lulin Mountain, leading to WSIIs in forms such as (NH₄)₂SO₄, NH₄HSO₄, (NH₄)₃H(SO₄)₂, NH₄NO₃, and NO₃⁻ aerosols not bound with NH₄⁺.
In summary, the high concentrations of NO₃⁻ in Douliu City’s PM2.5 were primarily driven by photochemical reactions of NOₓ with OH radicals and nocturnal heterogeneous reactions. In contrast, the elevated PM2.5 levels at Lulin Mountain were predominantly influenced by transported biomass burning plumes, with valley winds playing a secondary role. |
